In heating multi-level structures, the flow of warm air rising up stairways reduces the heating requirement of the upper floors, while cool air falling increases the demand for heating on the lower level. Likewise, in cooling multi-level structures, the flow of warm air rising up stairways increases the cooling requirement of the upper levels while decreasing the demand for cooling on the lower level. The end result is that the greater portion of warm air in the space resides in the upper levels, while the greater portion of cool air resides in the lower level. This stratification of temperature across multiple levels can be problematic for conventional heating and cooling systems, which substantially distribute conditioned air evenly through out multiple levels. For this reason, separate heating and cooling systems are often installed and employed to supply conditioned air to each level as needed. Where an upper level is often warmer than the lower level, a lower level heating system would typically operate more during the winter than an upper level heating system, and an upper level cooling system would operate more during the summer than a lower level cooling system. However, installing and operating a heating and cooling system for each level is more costly than installing only one heating and cooling system with sufficient capacity. Previous attempts have also been made to employ individual zone dampers at various vent outlets to supply conditioned air to only those zones that require air conditioning (eg.—upper level zones). However, zoning systems can also involve considerable costs associated with installing zone dampers and zone temperature sensors in each room of an existing home, where a conventional heating and cooling system may comprise as many as eight or more vent outlets in a multi-level space.